import java.security.MessageDigest;

public   class  MD5andKL {  
 // MD5加码。32位   
 public   static  String MD5(String inStr) {  
  MessageDigest md5 = null ;  
  try  {  
   md5 = MessageDigest.getInstance("MD5" );  
  } catch  (Exception e) {  
   System.out.println(e.toString());  
   e.printStackTrace();  
   return   "" ;  
  }  
  char [] charArray = inStr.toCharArray();  
  byte [] byteArray =  new   byte [charArray.length];  
  
  for  ( int  i =  0 ; i < charArray.length; i++)  
   byteArray[i] = (byte ) charArray[i];  
  
  byte [] md5Bytes = md5.digest(byteArray);  
  
  StringBuffer hexValue = new  StringBuffer();  
  
  for  ( int  i =  0 ; i < md5Bytes.length; i++) {  
   int  val = (( int ) md5Bytes[i]) &  0xff ;  
   if  (val <  16 )  
    hexValue.append("0" );  
   hexValue.append(Integer.toHexString(val));  
  }  
  
  return  hexValue.toString();  
 }  
  
 // 可逆的加密算法   
 public   static  String KL(String inStr) {  
  // String s = new String(inStr);   
  char [] a = inStr.toCharArray();  
  for  ( int  i =  0 ; i < a.length; i++) {  
   a[i] = (char ) (a[i] ^  't' );  
  }  
  String s = new  String(a);  
  return  s;  
 }  
  
 // 加密后解密   
 public   static  String JM(String inStr) {  
  char [] a = inStr.toCharArray();  
  for  ( int  i =  0 ; i < a.length; i++) {  
   a[i] = (char ) (a[i] ^  't' );  
  }  
  String k = new  String(a);  
  return  k;  
 }  
   
 // 测试主函数   
 public   static   void  main(String args[]) {  
  String s = new  String( "a" );  
  System.out.println("原始："  + s);  
  System.out.println("MD5后："  + MD5(s));  
  System.out.println("MD5后再加密："  + KL(MD5(s)));  
  System.out.println("解密为MD5后的："  + JM(KL(MD5(s))));  
 }  
}  